Investigation of glucose-modified liposomes using polyethylene glycols with different chain lengths as the linkers for brain targeting

Figures & data

Table 1 The size and Zeta-potential of different coumarin 6-loaded liposomes (n = 3)

	Molar ratio of lipids	Average size (nm)	Polydispersity index (PDI)	Zeta-potential (mV)
LIP	PC:cholesterol (2:1)	158.0 ± 7.1	0.172 ± 0.028	−60.4 ± 12.3
GLU200-LIP	PC:CHO-PEG200-GLU (2:1)	86.3 ± 5.7	0.270 ± 0.015	−33.3 ± 3.5
GLU400-LIP	PC:CHO-PEG400-GLU (2:1)	81.5 ± 6.3	0.252 ± 0.016	−36.2 ± 2.6
GLU1000-LIP	PC:CHO-PEG1000-GLU (2:1)	100.0 ± 5.0	0.265 ± 0.032	−24.9 ± 2.8
GLU2000-LIP	PC:CHO-PEG2000-GLU (2:1)	104.9 ± 8.7	0.289 ± 0.013	−20.9 ± 2.4

Abbreviations: LIP, liposomes; GLU, glucose; PC, phospholipid; CHO, cholesterol.

Figure 1 The variation in transmittancy versus the different incubation time of liposomes at the wavelength of 750 nm when incubated with phosphate-buffered saline containing 10% (v/v) fetal bovine serum for 24 hours at 37°C (n = 3).

Abbreviations: GLU, glucose; LIP, liposomes.

Figure 2 Fluorescein sodium leakage test of the ACs, BCECs, and the BBB model in vitro. The blank inserts were employed as controls (n = 3).

Abbreviations: ACs, astrocytes; blood–brain barrier; BCECs, brain capillary endothelial cells.

Figure 3 The accumulated cleared volumes of different coumarin 6-loaded liposomes on the blood–brain barrier model in vitro (n = 3).

Abbreviations: GLU, glucose; LIP, liposomes.

Figure 4 In vivo imaging of the mice that were anesthetized at 2 hours, 6 hours, and 12 hours after intravenous injection of different DIR-loaded liposomes respectively.

Notes: Color bar indicates the intensity of the nearinfrared fluorescence signal.

Abbreviations: DIR, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine; GLU, glucose; LIP, liposomes.

Figure 5 Ex vivo imaging in the mouse brain 1 hour after the intravenous injection of different DIR-loaded liposomes.

Note: The nearinfrared fluorescence signal intensity is weaker towards the left and stronger towards the right.

Abbreviations: DIR, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine; GLU, glucose; LIP, liposomes.

Figure 6 Confocal laser scanning microscopy images of the mouse brain frozen sections 1 hour after the intravenous injection of different coumarin 6-loaded liposomes.

Note: The scale bar is 75 μm on the lower right corner in each image.

Abbreviations: GLU, glucose; LIP, liposomes.

Figure 7 The distributions in different organs 1 hour after the intravenous injection of different coumarin 6-loaded liposomes (n = 3).

Notes: *P < 0.05 compared with LIP; **P < 0.01 compared with LIP; ***P < 0.001. compared with LIP.

Abbreviations: GLU, glucose; LIP, liposomes.

Scheme 1 Reagents and conditions: (a) TsCl, pyridine, 50°C, overnight; (b) HOCH₂ (CH₂OCH₂)₃ CH₂OH, dioxane, reflux, 8 hours; (c) MsCl, Et₃ N, THF, rt, 4 hours; (d) PEGs (PEG200, PEG400, PEG1000, PEG2000), NaH, THF, reflux, overnight; (e) succinic anhydride, pyridine, 75°C, 8 hours; (f) DCC, DMAP, 1,2,3,4-tetra-O-trimethylsilyl-D-glucopyranose, dichloromethane, rt, overnight; (g) TFA, THF, rt, 1 hour.

Abbreviations: TsCl, 4-toluenesulfonyl chloride; THF, tetrahydrofuran; DCC, dicyclohexylcarbodiimide; DMAP, 4-dimethylaminopyridine; TFA, trifluoroacetic acid.